[PATCH 4/3] start the global /sbin/init with 0,0 special pids

[PATCH 4/3] start the global /sbin/init with 0,0 special pids

[Oleg Nesterov]

As Eric pointed out, there is no problem with init starting with sid == pgid
== 0, and this was historical linux behavior changed in 2.6.18.

Remove kernel_init()->__set_special_pids().

This change and the previous change in daemonize() mean that /sbin/init does
not need the special "session != 1" hack in sys_setsid() any longer. We can't
remove this check yet, we should cleanup copy_process(CLONE_NEWPID) first, so
update the comment only.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>

--- PT/init/main.c~4_glob_init	2007-11-26 16:56:24.000000000 +0300
+++ PT/init/main.c	2007-11-27 15:21:56.000000000 +0300
@@ -829,7 +829,6 @@ static int __init kernel_init(void * unu
 	 */
 	init_pid_ns.child_reaper = current;
 
-	__set_special_pids(task_pid(current));
 	cad_pid = task_pid(current);
 
 	smp_prepare_cpus(max_cpus);
--- PT/kernel/sys.c~4_glob_init	2007-11-26 17:42:40.000000000 +0300
+++ PT/kernel/sys.c	2007-11-27 16:58:38.000000000 +0300
@@ -1054,12 +1054,11 @@ asmlinkage long sys_setsid(void)
 	if (group_leader->signal->leader)
 		goto out;
 
-	/* Fail if a process group id already exists that equals the proposed
-	 * session id.
+	/* Fail if a process group id already exists that equals the
+	 * proposed session id.
 	 *
-	 * Don't check if session == 1 because kernel threads and CLONE_NEWPID
-	 * tasks use this session id and so the check will always fail and make
-	 * it so init cannot successfully call setsid.
+	 * Don't check if session == 1, clone(CLONE_NEWPID) creates
+	 * this group/session beforehand.
 	 */
 	if (session != 1 && pid_task(sid, PIDTYPE_PGID))
 		goto out;

Re: [PATCH 4/3] start the global /sbin/init with 0,0 special pids

[Eric W. Biederman]

Oleg Nesterov <oleg@tv-sign.ru> writes:

> As Eric pointed out, there is no problem with init starting with sid == pgid
> == 0, and this was historical linux behavior changed in 2.6.18.
>
> Remove kernel_init()->__set_special_pids().
>
> This change and the previous change in daemonize() mean that /sbin/init does
> not need the special "session != 1" hack in sys_setsid() any longer. We can't
> remove this check yet, we should cleanup copy_process(CLONE_NEWPID) first, so
> update the comment only.

I guess that works.  As long as we get there.  We just need one more patch
in this series to fix the copy_process(CLONE_NEWPID).

Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>

Re: [PATCH 4/3] start the global /sbin/init with 0,0 special pids

[Pavel Emelyanov]

Eric W. Biederman wrote:
> Oleg Nesterov <oleg@tv-sign.ru> writes:
> 
>> As Eric pointed out, there is no problem with init starting with sid == pgid
>> == 0, and this was historical linux behavior changed in 2.6.18.
>>
>> Remove kernel_init()->__set_special_pids().
>>
>> This change and the previous change in daemonize() mean that /sbin/init does
>> not need the special "session != 1" hack in sys_setsid() any longer. We can't
>> remove this check yet, we should cleanup copy_process(CLONE_NEWPID) first, so
>> update the comment only.
> 
> I guess that works.  As long as we get there.  We just need one more patch
> in this series to fix the copy_process(CLONE_NEWPID).

I hope this will NOT be the fix that creates the namespace's 
init with the pid == 0 ;)

> Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>

Re: [PATCH 4/3] start the global /sbin/init with 0,0 special pids

[Eric W. Biederman]

Pavel Emelyanov <xemul@openvz.org> writes:

> Eric W. Biederman wrote:
>> Oleg Nesterov <oleg@tv-sign.ru> writes:
>> 
>>> As Eric pointed out, there is no problem with init starting with sid == pgid
>>> == 0, and this was historical linux behavior changed in 2.6.18.
>>>
>>> Remove kernel_init()->__set_special_pids().
>>>
>>> This change and the previous change in daemonize() mean that /sbin/init does
>>> not need the special "session != 1" hack in sys_setsid() any longer. We can't
>>> remove this check yet, we should cleanup copy_process(CLONE_NEWPID) first, so
>>> update the comment only.
>> 
>> I guess that works.  As long as we get there.  We just need one more patch
>> in this series to fix the copy_process(CLONE_NEWPID).
>
> I hope this will NOT be the fix that creates the namespace's 
> init with the pid == 0 ;)

No just with session == pgrp == (unchanged and thus with vpid 0).

Eric